Disc drives are the primary devices employed for mass storage of computer programs and data. Disc drives typically use rigid discs, which are coated with a magnetizable medium to form a recording layer in which data can be stored in a plurality of circular, concentric data tracks. Disc drives employ read/write heads that includes a reader for reading data from the data tracks and a writer for writing data to the data tracks.
Typical readers include a magnetoresistive or giant magnetoresistive read element that is adapted to read magnetic flux transitions recorded to the tracks, which represent bits of data. The magnetic flux from the recording medium causes a change in the electrical resistivity of the read element, which can be detected by measuring a voltage across the read element in response to an applied sense current. The voltage measurement can then be decoded to determine the recorded data. The writer includes a conducting coil configured to generate a magnetic field that aligns the magnetic moments of the recording layer to represent the desired bits of data.
There is a never-ending demand for higher data storage capacity in disc drives. One measure of the data storage capacity is the areal density of the bits at which the disc drive is capable of reading and writing. The areal density is generally defined as the number of bits per unit length along a track (linear density and units of bits per inch) multiplied by the number of tracks available per unit length in the radial direction of the disc (track density and units of track per inch or TPI). Currently, there is a need for areal densities on the order of 100 gigabits per square inch, which requires a track density on the order of 100-200 kTPI and greater.
In order to meet such high areal recording density demands read/write heads are formed smaller. Additionally, an active region of an air-bearing surface (ABS) of the head, where data reading and writing operations occur, is positioned closer to the recording medium (reduced head-medium separation). The heads are also configured to operate at higher frequencies which translates into an increase in current that is applied to the power that is applied to the heads. As a result, a greater amount of heat is generated within the heads, which can degrade their performance. For example, high local temperature concentrations in a head cause the materials of the reader and writer to expand. The resulting local stresses that are generated in the reader and writer can deform the shape of the head. This thermally induced expansion of the head can degrade data reading and writing performance by varying the head-media spacing, particularly at the active region of the ABS.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.